California needs reliable, zero-carbon energy to power the state and meet its climate goals, yet the last remaining nuclear power plant in the state, Diablo Canyon, is set to close. Investor-owned utility PG&E made the decision in 2016 to allow the licenses for the plant's two reactors to expire. They will shut down in 2024 and 2025.

Diablo Canyon has been producing about 8% of the electricity used in California. It is a zero-carbon energy source that's steady and reliable when the sun goes down, when the wind doesn't blow and when drought conditions reduce the output of large hydroelectric plants. In July, as a wildfire in Oregon threatened transmission lines on which California relies for imported electricity, the Diablo Canyon nuclear plant was essential to keeping the state's lights on.

When Diablo begins to shut down, what will replace the energy it produces? That's still a work in progress.

The California Public Utilities Commission issued an order to utilities demanding that they buy a massive amount — a total of more than 14,000 megawatts — of renewable energy and battery storage in the coming years. However, that may not be sufficient to prevent electricity shortages in the hot summer months, according to the California Energy Commission and the state's grid operator.

The Biden administration may get involved. On Tuesday, Energy Secretary Jennifer Granholm said she thinks "there is a change underfoot about the opinion that people may have about nuclear" and she said she would be willing to talk with state officials about keeping Diablo open. Also on Tuesday, the Biden administration said it is actively searching for communities that would be willing to do their part to fight climate change by hosting nuclear waste sites. Then "those communities that have nuclear facilities won't have to worry about that problem," Granholm said.

We'll keep checking in to see how that search is coming along, but in the meantime, California has to figure out how to procure enough electricity to meet the needs of the state's residents and businesses without the perpetual risk of dangerous power outages. In addition to shutting down Diablo Canyon, the state is phasing out four electricity-generating plants that run on natural gas. They are all scheduled to be closed by the end of 2023, if not sooner.

In the scramble to procure more renewable energy, there has not been much discussion of the cost to ratepayers. Southern California Edison estimated in 2019 that it could cost up to $250 billion to meet the state's goal of carbon neutrality by 2045. It would not be surprising if state regulators allowed utilities to recoup those billions of dollars through higher rates or surcharges.

An honest public discussion of the cost and limitations of solar, wind and battery-storage energy would be helpful as the state works through these challenges. Solar and wind energy will always be intermittent, and large-scale batteries that can supply power for longer than four hours are still in development.

Nuclear power has serious challenges, too. The dangerous waste-storage problem has simply not been solved, anywhere in the world. But if the goal is zero-carbon energy that is reliable and affordable, keeping Diablo Canyon open beyond 2024 and 2025 makes sense. Ultimately, the future of the nuclear plant is up to its owner, PG&E. However, public officials would be wise to do what they can to extend the life of Diablo Canyon until other renewable energy sources can stand on their own.